Locomotive draught is induced up to 10" of water-head, and
forced up to 2" by the current entering the front of ashpan.
P. 698. Mechanical Stoking.—It is well known that
hand firing is responsible for a large quantity of imperfectly-burned
fuel, as well* as the emission of much smoke, and some form of
machine stoking is therefore desirable, whose expected advantages-
would be (i) smoke-prevention by uniform firing and constantly
closed doors, (2) economy of fuel by using cheap coal and
obtaining more perfect combustion, (3) economy of labour, (4)
higher, more uniform, and more easily regulated evaporation.
There are two forms of these machines : coking stokefs, where the
coal is first fed to a dead-plate or its equivalent, for preliminary
distillation ; and sprinklers, where the fine coal enters at the centre
of the bars and is distributed by fans or beaters. We have only
space for an example of the first, Fig. 873, as made by the New
Conveyor Company. The hoppers A A contain small coal, placed
there by mechanical elevators. This coal is fed slowly forward by
the screw B, then coked at c, and pushed forward gradually by
the movement of the firebars, which are connected to the crank
shaft ix Finally the fuel arrives at E completely burnt, and simply
drops down as ash.